1. Field of the Invention
The present invention relates to a load control system comprising a plurality of load control devices for controlling the amount of power delivered to a plurality of electrical loads from an AC power source, and more particularly, to a lighting control system for shedding lighting loads in response to a command received via a network, such as the Internet.
2. Description of the Related Art
Reducing the total cost of electrical energy is an important goal for many electricity consumers. The customers of an electrical utility company are typically charged for the total amount of energy consumed during a billing period. However, since the electrical utility company must spend money to ensure that its equipment (e.g., an electrical substation) is able to provide energy in all situations, including peak demand periods, many electrical utility companies charge their electricity consumers at rates that are based on the peak power consumption during the billing period, rather than the average power consumption during the billing period. Thus, if an electricity consumer consumes power at a very high rate for only a short period of time, the electricity consumer will face a significant increase in its total power costs.
Therefore, many electricity consumers use a “load shedding” technique to closely monitor the amount of power presently being consumed by the electrical system. Additionally, the electricity consumers “shed loads”, i.e., turn off some electrical loads, if the total power consumption nears a peak power billing threshold set by the electrical utility. Prior art electrical systems of electricity consumers have included power meters that measure the instantaneous total power being consumed by the system. Accordingly, a building manager of such an electrical system is able to visually monitor the total power being consumed. If the total power consumption nears a billing threshold, the building manager is able to turn off electrical loads to reduce the total power consumption of the electrical system.
Many electrical utility companies offer a “demand response” program to help reduce energy costs for their customers. With a demand response program, the electricity consumers agree to shed loads during peak demand periods in exchange for incentives, such as reduced billing rates or other means of compensation. For example, the electricity utility company may request that a participant in the demand response program shed loads during the afternoon hours of the summer months when demand for power is great. Some prior art lighting control systems have offered a load shedding capability in which the intensities of all lighting loads are reduced by a fixed percentage, e.g., by 25%, in response to an input provided to the system. The input may comprise an actuation of a button on a system keypad by a building manager. Such a lighting control system is described in commonly-assigned U.S. Pat. No. 6,225,760, issued May 1, 2001, entitled FLUORESCENT LAMP DIMMER SYSTEM, the entire disclosure of which is hereby incorporated by reference.
Electrical utility companies have sought, for many years, to encourage customers to shed load during periods of peak demand, but have been faced with many challenges. For example, the utility companies have had difficulty successfully communicating a command to shed load to the customers, for example, via radio-frequency (RF) signals or via a modem. Typically, the electrical utility companies do not have a direct means to know if the customer has actually reduced load, and thus, the electrical utility companies have not been able to monitor that the customer has actually shed loads. For example, when a radio signal is sent out, there is no way for the power company to tell if a specific customer has actually changed loads to reduce the power consumption. Further, the electrical utility companies have also had trouble ensuring that the communications with the customer are secure.
The fundamental problem with previous strategies for electronically communicating load shed commands from the electrical utility company to the customers has been that the communications (i.e., RF signals or transmissions via the Internet) with the customer have been initiated at the electrical utility company. In other words, the electrical utility company attempts to send a signal to a device inside the customer's premises to transmit a load shed command. Since the security of computer systems is a major concern of most commercial customers, most customers are wary providing access to their computer systems to outside vendors, such as the electrical utility company. If the electrical utility company can get through the firewall of a customer to turn the lights off, a computer hacker may also be able to get in.